1. Field of the Invention
This invention relates to the field of hydraulic systems, and deals more particularly with such systems for raising and lowering aircraft landing gear without access to an external power source.
2. Description of the Prior Art
Aircraft landing gear is raised and lowered through operation of hydraulic actuators pressurized by a fluid pump driven from the aircraft engines. Failure of the engines in flight or loss of the fluid pressure source for any other reason during flight requires a secondary source of power to open the landing gear doors, lower the gear and lock the gear in position against collapse when bearing weight of the aircraft, on impact during landing.
Conventionally hydraulic actuators, capable of extension in length and retraction in response to pressure produced by the fluid pressure source, are used to raise and lower the landing gear.
Various techniques have been developed to deal with an in-flight loss of power and to lower the gear in this condition. U.S. Pat. No. 4,108,402 describes an auxiliary system involving a parachute canopy energized by the pilot for supporting an aircraft in the event of power failure.
U.S. Pat. No. 3,107,866 describes a hydraulic system for coordinating sequential operation of a wheel well door and a landing gear. U.S. Pat. No. 3,224,713 describes an electronic system intended to prevent gear-up landing incidents resulting from premature retraction of the gear after takeoff and where the gear is inadvertently raised while the aircraft is on the ground.
Shock absorber for dissipating energy from impact loads on landing are described in U.S. Pat. Nos. 4,508,201; 4,506,869; 4,437,548; 4,405,119; and 4,372,545. None of these pertains to an actuator for storing a pressurized charge for use in lowering the gear in the event of in-flight loss of power.